The thesis will consist of a series of 5 studies which aim to investigate the functional role of phasic events in sleep. K complexes and spindles are phasic events occurring in sleep whose role may be examined using neurophysiological methods such as averaged event- related potentials (ERPs), power spectral analysis (PSA), and voltage- distribution brain mapping. Two studies have been completed thus far. The first study established the ERP as a reliable measure of the extent of information processing during sleep. More specifically, decreased negativity in the ERP paralleled lengthened reaction times associated with the loss of consciousness at sleep onset. The second study demonstrated an inhibitory role for sleep spindles, by measuring the effects of high intensity auditory stimuli on information precessing during spindle activity. Next, we are proposing to further investigate the nature of this finding, by quantifying the temporal and topographic characteristics of the inhibition associated with sleep spindles. The fourth study will investigate the functional role of the K-complex in information processing during sleep, in order to determine whether it exists to protect sleep from disturbance or to alert the sleeper to the environment. Lastly, subsequent analysis of data collected in the preceding studies will investigate the occurrence of K-spindle activity, the phenomena where these phasic event occur together. These studies will elucidate the functional role of phasic events in sleep and thereby lead to a further understanding of normal sleep processes and various sleep pathologies.